What is a ceramic foam filter used for?

Ceramic foam - Wikipedia

Ceramic foam is a resilient material crafted from ceramics. The production methods include impregnating open-cell polymer foams with ceramic slurry and subsequently firing them in a kiln, leaving behind only the ceramic material. The foams can comprise various ceramic materials, such as aluminum oxide, a commonly-used high-temperature ceramic, which gets its insulating properties from the numerous tiny air-filled voids within the material.

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The foam is multifunctional, suitable for thermal insulation as well as acoustic insulation, pollutant absorption, molten metal alloy filtration, and as substrate for catalysts requiring a large internal surface area. It has also been utilized as a stiff, lightweight material for supporting reflecting telescope mirrors.

Properties

Ceramic foams are hardened ceramics containing air or other gases trapped within pores throughout the material. Due to their ability to create a large specific surface area, these materials can be fabricated with up to 94-96% air by volume and withstand temperatures as high as 1700°C. Because many ceramics are made from oxides or other inert compounds, there is minimal risk of oxidation or reduction. Historically, pores were avoided in ceramic components due to their brittleness, but in practice, ceramic foams demonstrate high strength and plastic toughness, outperforming bulk ceramics in certain applications by blunting crack tips and reducing failure likelihood.

Preparation Methods

Organic Foam Impregnating Method

Widely used in the industry, this method involves creating ceramic foam with a 3D mesh skeleton by coating a polyurethane organic foam mesh body with ceramic slurry. The body is then dried at room temperature, and the mesh is burnt away to leave the ceramic foam. This method is particularly effective for preparing silicon carbide foam ceramics.

Foaming Method

This method employs a chemical reaction to generate volatile gas that foams the slurry. The slurry is dried and sintered to obtain ceramic foam, with the product's shape and density controllable through this method, making it suitable for producing small pore size closed-cell ceramics.

Manufacturing

Several accepted methods exist for creating ceramic foams, with one of the earliest and most common being the polymeric sponge method. A polymeric sponge is coated with a ceramic suspension, rolled to fill pores, dried, and pyrolyzed to decompose the polymer, leaving a porous ceramic structure. This structure is then sintered for final densification. Direct foaming methods also exist, though they are challenging due to the thermal instability of wet foams.

A new technique for creating aluminum oxide foams has been developed, involving heating crystals with metal until polymer chains form, causing the mixture to separate. Air bubbles trapped during this process are locked in place, forming the foam as the material is heated and the polymer is burned off.

Uses

Insulation

Due to their extremely low thermal conductivity, ceramic foams are used as insulation materials. Composed of common compounds such as aluminum oxide, they are safe to use and possess high strength and hardness, making them suitable for low-stress structural applications.

Electronics

Ceramic foams are increasingly used in electronics due to their easily controlled porosities and microstructures. They serve as electrodes and scaffolds for solid oxide fuel cells and batteries and function as cooling components by separating pumped coolant from circuits. Materials like silica, aluminum oxide, and aluminum borosilicate fibers are commonly used for these applications.

Pollution Control

Ceramic foams are effective in pollutant control, particularly for capturing and oxidizing particulates from engines. They can support catalysts that induce oxidation throughout the foam, enhancing their effectiveness.

Filtering

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Ceramic foam filters (CFF) are used to filter liquid metal, reducing impurities such as nonmetallic inclusions and improving the final product's quality in continuous casting, semi-continuous casting, and casting gating systems.

Wastewater Treatment

With their unique pore structure and large specific surface area, ceramic foams are used for wastewater filtration. This process involves adsorption, surface filtration, and deep filtration, with deep filtration being the primary method.

Construction

Close-cell ceramic foam provides excellent insulation for walls and roofs, resisting corrosion and absorbing sound. In China, ceramic foam is used as a thermal insulation material in buildings.

Noise Reduction

Ceramic foams are employed to absorb sound in wet and oily environments by transforming sound wave energy into heat through friction and air resistance, thus reducing echoes.

Automobile

Ceramic foam is used in catalytic converters in exhaust systems because of its high temperature resistance and thermal stability, aiding in the removal of particulates and oxides from exhaust gases.

Biomaterial

Research shows promise for ceramic foams combined with Bioglass in creating tissue scaffolds for bone repair. Their porosity allows for cell migration, high mechanical strength supports load-bearing functions, and bioactivity encourages cell proliferation.

How to Use Ceramic Foam Filter Plate

Ceramic Foam Filter Plates are made of alumina, silicon carbide, and zirconia. They are used to remove large inclusions in molten aluminum and absorb micron-sized particles, improving surface quality and product performance in aluminum profile, foil, and alloy production.

Instructions:

1. Clean the filter box.
2. Place the filter plate gently into the box and seal it to prevent leakage.
3. Preheat the equipment and filter to match the temperature of the molten aluminum for 15–30 minutes to remove moisture and facilitate filtration.
4. Monitor changes in hydraulic head during casting and ensure the launder is filled with aluminum water.
5. Avoid knocking the filter plate during filtration and ensure the launder is filled with aluminum water to minimize disturbance.
6. Remove the ceramic foam filter promptly after use and clean the filter box.

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